1. Field of the Invention
The present invention relates to a method for modifying a gas turbine single plant into a combined cycle plant comprising a combination of the gas turbine, a waste heat recovery boiler and a steam turbine and a method for re-using a used high temperature denitration catalyst of the gas turbine single plant as an intermediate temperature denitration catalyst of other modified, existing or new plants, and also relates to a re-produced catalyst.
2. Description of the Prior Art
Recently, in order to cope with an urgent demand for electric power, there are often constructed gas turbine single plants that are excellent in operability and constructible with less investment cost and over a shorter period. However, the gas turbine single plant is less excellent in long term plant efficiency, and hence it is effective that a gas turbine single plant is first constructed to be modified in the future by re-powering work into a combined cycle plant that is excellent in plant efficiency. (See Patent Document 1 below, for example.)
On the other hand, in denitration equipment that is installed for denitration of the exhaust gas in a power plant or the like, there is used a catalyst that contains TiO2 (titanium oxide) as a main component and includes at least one of WO3 (tungsten oxide) and MoO3 (molybdenum oxide) and further includes V2O5 (vanadium oxide).
In the gas turbine single plant, as the temperature of the exhaust gas to be denitrified is as high as 450 to 600° C., a high temperature denitration catalyst is used. In the high temperature denitration catalyst, V2O5 that is vulnerable at the high temperature is used only in a minute amount or no V2O5 is included. (See Patent Document 2 below, for example.)
That is, the denitration catalyst containing the minute amount or none of V2O5 component is a catalyst that is optimized for high temperature. Hence, if the gas turbine single plant is once re-powered into a combined cycle plant as mentioned above, this high temperature denitration catalyst cannot be used for the combined cycle plant in which the temperature of the exhaust gas to be denitrified is an intermediate temperature of 200 to 450° C.
For the reason as explained above, when the gas turbine single plant is to be re-powered into the combined cycle plant, the high temperature denitration catalyst that has been used in the gas turbine single plant is wasted and an intermediate temperature denitration catalyst must be newly adopted for the combined cycle plant. This invites an increase in the investment cost of the plant.
Patent Document 1                Japanese laid-open patent application 1996-260912        (Paragraphs 0004, 0005 and 0009 to 0018)        
Patent Document 2                Japanese laid-open patent application 1994-079139                    (Paragraphs 0013 to 0018)                        